The formation of postoperative intraperitoneal adhesions, the pathological adherence of organs and tissue surfaces, is the leading cause of intestinal obstruction following abdominal surgery (H. Ellis, Surg. Gynec. Obstec., 133 [1971]). An adhesion typically comprises organized fibrinous exudate projected on the surface of a serous membrane which connects or adheres the opposing surfaces of tissues or organs. It is also the major factor contributing to infertility after reconstructive tubal surgery (Buttram, V. C., Fert. and Ster. 40:5 [1983]). It has been reported that 50-90% of all persons undergoing abdominal surgery develop adhesions (Colleti, L. and Bassart, B. Arch. Surg. Fert. 88: 774 [1964]). Adhesion formation has also been observed following intraabdominal infection (Hau, T. et al., Surg. Gyn. & Ob. 148:415-418 [1979]). Adhesion formation has also been observed following tendon surgery (Weiss, C. et al., Bull. Hosp. Joint Diseases 47(1), 31 [1987].).
From the earliest days of abdominal surgery, surgeons became aware of fibrinous adhesions which stuck loops of intestinal and other abdominal viscera to one another within a few hours of surgery, inflammation or trauma. The fibrinous exudate can either reabsorb completely, leaving a clear peritoneal cavity, or become organized with an in growth of capillaries and fibroblasts to form established fibrous adhesions. The important question, which to this day remains unanswered, is what factor determines whether or not the fibrinous exudate is absorbed or organized. A theory has been developed that adhesion formation is a consequence of the destruction of the peritoneal endothelium. Numerous studies have refuted this theory. (See e.g., Ellis, H. Brit. J. Surg., 50:10 [1962]).
It has been shown that normal healing of peritoneal injuries or defects commences with formation of a fibrin matrix, followed by phagocytosis of that matrix by macrophages, monocytes, lymphocytes and polymorphs. Fibroblasts and collagen bundles are observed prior to the peritoneum taking on a normal appearance. The normal healing process takes approximately three (3) days. (Buckman, R. F. et al., J. Surg. Res. 21, 67 [1976]). Whether the fibrin matrix is reabsorbed appears to be related to whether the tissue was ischemic (Rubin, i.C., Surg. Obstet., 12:117 [1911]). Ellis, H. et al., Brit. J. Surg. 52:471 (1965) developed an ischemic peritoneal model and showed that 83% of ischemie injuries resulted in adhesion formation while only about 9% of the, non-ischemic models produced adhesions. Using electron microscopy, the fibroblastic invasion has been shown to arise from macrophages which infiltrate the area, and develop into fibroblasts, giant cells, and epithelial-like cells. (Eskeland, G., Acta Path. Microbiol. Stand., 62:459 [1964]). Adhesion formation according to Ellis acted as a vascular graft. Using a similar model to Ellis, Buckman et al., supra., showed that peritoneal defects have a high plasminogen activity which is lost in peritoneum rendered ischemic.
Fibrin deposition following bacterial infiltration of the peritoneal cavity is a defense mechanism in preventing septicemia. (Ahrenholz, D. H. and Simmons, R. L., Surgery 88: 41-47 [1980], Zinser, H. H. and Pryde, A. W., Ann. Surg. 136: 818 [1982]). The bacteria are contained, but the fibrin deposition often leads to abscess formation. (Ahrenholz and Simmons, supra.). Fibrin deposition occurs during early stages of peritonitis, when fibrinogen-rich exudate in the peritoneal cavity is converted to fibrin. (Hau, supra.). Post-operative intraabdominal abscesses are a potential source of infection and, ultimately, death. Peritonitis and its complications are associated with a high mortality rate. Amongst the elderly the mortality rate is in the range of 60-80%. (Hau, T. et al., Curr. Prob. Surg. 16: 1-65 [1979]).
Plasminogen activators present in both the mesothelium and submesothelial blood vessels of the peritoneum are responsible for lysing and removing intraperitoneal fibrin deposits. (Porter, J. M. et al., L. Surg. Forum 20:80 [1969]; Buckman, R. F. et al., J. Surg. Res. 20:1 [1976]). Serosal or peritoneal injury such as inflammation or trauma results in the formation of an exudate of cellular components and fibrin through tears in the small veins of the traumatized area (Aurora, A. L. et al. Indian J. Med. Res. 62: [1972]) as well as a local decrease in fibrinolytic activity. (Buckman, R. F. supra.) It has been shown that when local fibrinolytic activity is reduced by 50% or more, fibrin cannot be cleared and permanent adhesions form. (Gervin, A. S. et al., Am. J. Surg. 125 [1973]).
Numerous papers have been published describing efforts to prevent adhesion formation. Various prophylactic methods have been tried to prevent fibrin deposition and adhesions. Prevention of the deposition of fibrin in the peritoneal exudate has involved the use of sodium citrate, heparin, and other anticoagulants. In removal of the fibrin which already has formed, a variety of enzymes have been used, for example, trypsin, pepsin, papain, hyaluronidase, streptokinase and streptodornase. Other approaches for fibrin removal use such salts as sodium ricinoleate or lavage for mechanical removal of fibrin.
Heparin and dicumarol were the first agents used to prevent fibrin deposition. (Lehman, E. P. and Boys, F. Ann. Sur., 112:969 [1940]; White, B. H. Ann. Surg., 130:942 [1949]). Deaths and postoperative hemorrhage were reported in those patients receiving heparin. More recently, the antithrombogenic property of dextran has led to its use to prevent adhesions. (Choate, W. H. et al., Arch. Surg., 88:249 [1964]). Intraperitoneal dextran was found to decrease the severity of the adhesions but did not prevent formation (Kapur, B. M. L. et al., Indian J. Med. Res., 56:1406 [1968]). Oral administration of the anti-inflammatory agent oxyphenbutazone was also used to reduce adhesion formation. (Kapur, B. M. L., et al., Arch. Surg., 98:301 [1969]).
Lavage with saline, dextrose, or particularly a hypertonic dextrose solution has been suggested, but the rapid absorption of such solutions rendered them ineffective. (Buchbinder, J. R., Surg. Gynec. Obstet., 45:769 [1927]; Totten, H. P., Surgery, 8:456 [1940]). Digestive enzymes such as pepsin and trypsin were thought to have utility by destroying fibrin. However, these substances are both rapidly neutralized by peritoneal exudates and were shown to be ineffective. (Kubota, T., Japan M. World, 11:226 [1922]). Papain a proteolytic enzyme was also tried but found to be neutralized by the peritoneal exudate. Papain was also administered orally and found to reduce the severity of the adhesions, but not the incidence. (Kapur, B. M. L., et al., Arch. Surg., 98:301 [1969]). Intraperitoneal administration of papain in rats had no effect on adhesion formation. (Stevens, L. E., Amer. J. Surg., 115:535 [1968]).
A number of fibrinolytic agents have been tested to prevent adhesions. The fibrinolytic system is typically understood to mean that system in blood which involves the conversion of plasminogen to plasmin. A natural plasminogen activator interacts with plasminogen to convert the precursor to plasmin which then lyses cross-linked fibrin. Exogenous activators such as streptokinase and urokinase also activate the conversion of plasminogen to plasmin. Thrombolytic agents include plasmin, and plasminogen activators such as streptokinase, streptodornase, and urokinase. These thrombolytic and fibrinolytic agents as well as other agents have been used to prevent fibrin deposition and remove adhesions. Initial work showed that streptokinase and streptodornase prevented traumatically induced adhesions in rabbits, but not in dogs. (Wright, L. T., et al., Proc. Soc. Exp. Biol. Med., 75:602 [1950]). In one study, it was observed that intraperitoneal therapy on three successive days was more effective than a single injection. (Knightly, J. J., et al. Surgery, 52:250 [1962]). Other studies were less favorable. In a series of experiments using intravenous and intraperitoneal administration of a variety of fibrinolytic enzymes in dogs, rabbits, and rats as well as different techniques to produce adhesions, no significant prophylactic or therapeutic effect was observed. (Jewett, T. C., et al., Surgery 57:280 [1965]). Highly purified preparations of streptokinase administered to rats in a single dose or multiple single injections on three successive days did not inhibit adhesion formation. (James, D. C. O., et al., J. Path. Bact. 90:279 [1965]). Additional studies using purified streptokinase in rabbits indicated that adhesions to areas of parietal injury could be inhibited by giving multiple injections of streptokinase in solution intraperitoneally on two or three consecutive days. (Id.) Thrombolytic therapy has been used to prevent fibrin deposition in endocarditis in a rabbit model. (Duraug, D. T., J. Path. 129:537 [1975]). Fibrinolytic agents have been used to reduce wound infections induced by infected plasma clots in guinea pig skin incisions. (Rodeheauer, G. et al., Am. J. Surg. 129:537-544 [1975]).
Other compounds which were observed to have a fibrinolytic effect have also been used to prevent adhesions. Protoporphyrin, which has a fibrinolytic action, was found to reduce the percentage of adhesions developing to laparotomy in the rat. (Iijima, N. et al., Postgrad. Med. J. 46:278 [1970]). Hyaluronidase, an enzyme which hydrolyzes hyaluronic acid, one of the polysaccharides constituting intercellular ground substance, has prevented adhesion formation in dogs when administered intraperitioneally at the same time that talc was applied to induce adhesion formation. (Connolly, J. E. and Richards, V. Surg. Forum, 2:85 [1951]). Other studies in rat following cecal crushing showed no reduction in the incidence of adhesions following intraperitoneal administration of hyaluronidase. (Thomas, J. et al., Proc. Soc. Exp. Biol. Med., 74:497 [1950]).
Dexamethasone, methylprednisolone, sodium succinate, promethazine hydrochloride and human fibrinolysin alone and in combination were administered intramuscularly or intraperitoneally to rats to prevent adhesion formation. (Gazziniga, A. G. et al., Arch. Surg. 110:429 [1975]). None of the agents alone eliminated adhesion formation. Methylprednisolone, promethazine and human fibrinolysin in combination intraperitoneally in a single dose appeared to eliminate adhesion formation. Id.
In addition to those substances mentioned above, others have been placed in the peritoneal cavity to prevent adhesion formation, including minced ox peritoneum, olive oil, eptnephrine solution, amniotic fluid and sodium ricinoleate. None of the substances have been shown to prevent adhesion formation or reformation.
An object of the present invention is to provide a composition preventing fibrin deposition or adhesion formation for use in various surgical and clinical contexts including, but not limited to, abdominal and pelvic surgery, abdominal infection, inflammation or trauma. Another object of the invention is to provide a composition that is easy and convenient to apply to the site of potential fibrin deposition or adhesion formation. Yet another object of this invention is to provide a method of preventing fibrin deposition or adhesion formation by topical application of the composition of this invention to the organs and/or surrounding tissues to which fibrin may be deposited or an adhesion may form. Still another object of this invention is to eliminate the introduction of nondegradable solids as a means for delivering agents for preventing fibrin deposition or adhesion formation. Another object is to provide enzymes for the prevention of fibrin deposition or adhesions in a form such that they are not inactivated by substances in the biological fluid. Yet another object is to provide such enzymes in a formulation enabling continuous release without any need for exogenous matrices or devices.